Several components commonly incorporated in cleaning products are temperature sensitive, such as perfumes, enzymes, bleaches, bleach activators and bleach catalysts.
By way of example, it is common to incorporate perfumes in cleaning products such as laundry wash products to impart a pleasant or fresh smell to the cleaned item. In the case of particulate wash products, it is known to incorporate the perfume in the form of microcapsules containing the perfume.
One method of making such microcapsules is disclosed in U.S. Pat. No. 5,066,419. This reference is concerned with detergent compositions which comprise one or more detersive surfactants, optionally one or more builders and perfume particles of the aforementioned kind. These particles are specifically defined as comprising a core having from about 5% to about 50% by weight of perfume dispersed in from about 95% to about 50% of a “carrier” material of solid fatty alcohol or fatty ester having a molecular weight and melting point. The core is coated with a water-insoluble friable coating. The preferred friable coating is of the urea or melamine plus aldehyde type. The resulting microcapsules have an average particle size less than about 350 microns, preferably not greater than 150 microns.
Formulation of perfumes in microcapsule form has several advantages. First, perfumes are by their nature, volatile. Second, if incorporated in a particulate product, there is the risk of loss of perfume efficacy by evaporation. Another reason is the risk of adverse interactions between the perfume and one or more other components in the product. These problems are overcome or at least mitigated by the microencapsulation technique. It also has the advantage that, depending on the form of microcapsule, in use, the possibility is provided for delayed or extended perfume release, for example in the case of deposition on a fabric in a wash liquor containing a detergent composition for fabrics washing.
Probably the oldest and longest used method of formulating particulate cleaning products is spray drying, whereby granules are formed by spraying a slurry of ingredients against a counterblast of warm air. Around the 1980s, the alternative granulation process of mechanical mixing granulation became popular, typically involving mixing to form granules and then densification of the granules so formed. In both cases, additional ingredients, especially ingredients which are incompatible with other components of the granule, are sometimes post-dosed either in powder or granule form to the base granule formed by spray drying or mechanical granulation.
In recent times, flexible manufacture of ranges of different products has involved making pre-granulated “adjuncts” rich in one or more ingredients such as surfactants or detergency builders or other ingredients such as enzymes or mixtures of such ingredients, then mixing them with other granulates and/or powdered ingredients according to the particular formulation required. In accordance with this manufacturing philosophy, it would be useful to provide adjuncts containing microencapsulated perfume. However, it has been found that use of conventional granulation techniques to provide such granulated adjuncts containing microencapsulated perfume leads to problems.
Specifically, it has been found that to granulate perfume microcapsules by spray drying, as taught US-A-2003/0125222, results in a poor particle size distribution with an undue proportion of fine material in the product. This is undesirable because of the tendency for such a product to segregate. The high temperature involved can also damage the microcapsules, leading to perfume loss.
Sugars have been proposed as water-dispersible binders in granules which contain calcite, non-soap surfactant and other optional ingredients commonly found in laundry cleaning products, as disclosed in U.S. Pat. No. 4,908,159. The highest level of sugar actually disclosed in this reference is 28.6% by weight of sucrose in a granule which additionally contains only calcite and anionic surfactant.
As described in U.S. Pat. No. 5,879,920, enzyme containing granules may be made by forming a core comprising a water soluble material coated with a vinyl polymer, covered with an enzyme layer with polyvinyl pyrrolidone and then another polymer outer layer. The core with its polymer coating contains a water soluble or dispersible material which may be inter alia, a sugar or dispersible starch. The core can constitute up to 85% by weight of the entire granule, up to 95% by weight of that core being the water-soluble or water dispersible material. The enzyme-containing layer may comprise from 5% to 70% by weight of the entire granule, of which the polymer content may represent from 0.1% to 5%.
Lower levels of sugars have also been used in the enzyme containing granules disclosed in EP-A-656 058, in order to improve dispersibility in the wash liquor.
According to US-A-2002/0123449, a highly water-soluble cyclodextrin is granulated with an inorganic compound such as a zeolite or other water soluble or insoluble inorganic detergency builder to form granules which are added to laundry washing powders to reduce malodour from fabrics in the wash. The cyclodextrin can be present up to 90% by weight of the granule.
The inventors have now discovered that the granules containing sensitive ingredients such as perfume microcapsules can be made using a mechanical granulation technique operating at a temperature/energy input low enough not to damage such ingredients by utilising relatively high levels of an organic water-soluble crystalline solid granulation auxiliary. For the avoidance of doubt, the term mechanical granulation technique excludes spray drying but does not preclude a mechanical granulation technique in which one or more of the starting materials are themselves the product of a spray-drying process. The term mechanical granulator is to be construed in like fashion.
Another possible advantage of granules according to the present invention is achieving an appropriate strength of the granules without significant loss of solubility as may occur with inorganic solid granulation auxiliaries.